Thulium-doped heavy metal oxide glasses for 2UM lasers

Abstract

A heavy metal oxide glass selected from germanate, tellurite and bismuth oxide glasses provides a host for highly efficient Thulium doped 2 μm oxide glass and fiber lasers. The concentration of Thulium ions is high enough that energy transferred by the phenomenon of cross-relaxation will enhance laser emission at 2 μm and suppress emission at 1.5 μm so that 2 μm emission is dominant.

Description

GOVERNMENT RIGHTS[0001]The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Grant No. NNL04AB40P.CROSS-REFERENCE TO RELATED APPLICATIONS[0002]This application claims benefit of priority under 35 U.S.C. 120 to U.S. application Ser. No. 10 / 783,480 entitled “Single-Frequency Narrow Linewidth 2 μm Fiber Laser” filed on Feb. 19, 2004 and issued as U.S. Pat. No. 7,106,762 on Sep. 12, 2006, the entire contents of which are incorporated by reference.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]This invention relates to glasses and fibers for laser applications and more specifically to Thulium-doped heavy metal oxide glasses for near 2 μm lasers with high quantum efficiency.[0005]2. Description of the Related Art[0006]2 μm lasers are highly transmissive in air, relatively eye-safe, and highly absorptive in many natural substances s...

AI Technical Summary

Benefits of technology

[0010]This is accomplished with a heavy metal oxide glass host selected from germanate, tellurite and bismuth oxide glasses. The host is heavily doped with Thulium ions, suitably at least 2×1020 ions / cm3, and preferably at least 4×1020 ions / cm3. Most typically, the Thulium ions will be introduced into the host glass as Thulium oxide of at least 2 wt. %, and preferably at least 4 wt. % to achieve the necessary ion concentrations and increase quantum efficiency. The concentration of Thulium ions is high enough that energy transferred by the phenomenon of cross-relaxation will enhance laser emission at 2 μm and suppress emission at 1.5 μm so that 2 μm emission is dominant. The quantum efficiency is preferably at least 100%, and most preferably at least 150%.

Problems solved by technology

Unfortunately crystalline materials are expensive and cannot be pulled into fibers, hence can only be used for free space solid-state lasers.

Unfortunately, neither glass is a good host for Thulium doped laser applications.

Silica glass has high phonon energy, approximately 1100 cm−1, and can only support limited doping concentrations, and thus exhibits poor quantum efficiency.

Although fluoride exhibits low phonon energy of about 700 cm−1 and accept high rare-earth doping concentrations, fluoride glass is physically weak and chemically not durable, which limits the output power of the laser and seriously restricts practical application.

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